Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$220.96	4.117%	$230.0569	$230.06	$230.05	$230.10
Purchase #2	$165.91	6.270%	$176.3126	$176.31	$176.30	$176.30
Purchase #3	$179.29	3.331%	$185.2621	$185.26	$185.25	$185.30
Purchase #4	$234.96	3.798%	$243.8838	$243.88	$243.90	$243.90
Purchase #5	$180.47	4.343%	$188.3078	$188.31	$188.30	$188.30
Purchase #6	$205.31	10.860%	$227.6067	$227.61	$227.60	$227.60
Purchase #7	$128.32	7.410%	$137.8285	$137.83	$137.85	$137.80
7 purchase totals =	$1,315.22		$1,389.2584	$1,389.26	$1,389.25	$1,389.30