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	$193.49	11.588%	$215.9116	$215.91	$215.90	$215.90
Purchase #2	$106.73	4.151%	$111.1604	$111.16	$111.15	$111.20
Purchase #3	$226.45	10.460%	$250.1367	$250.14	$250.15	$250.10
Purchase #4	$157.84	6.556%	$168.188	$168.19	$168.20	$168.20
Purchase #5	$120.85	7.644%	$130.0878	$130.09	$130.10	$130.10
Purchase #6	$165.41	13.781%	$188.2052	$188.21	$188.20	$188.20
Purchase #7	$82.60	4.482%	$86.3021	$86.30	$86.30	$86.30
7 purchase totals =	$1,053.37		$1,149.9918	$1,150.00	$1,150.00	$1,150.00