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	$91.31	5.488%	$96.3211	$96.32	$96.30	$96.30
Purchase #2	$124.42	9.213%	$135.8828	$135.88	$135.90	$135.90
Purchase #3	$197.51	5.586%	$208.5429	$208.54	$208.55	$208.50
Purchase #4	$236.50	7.522%	$254.2895	$254.29	$254.30	$254.30
Purchase #5	$96.40	13.859%	$109.7601	$109.76	$109.75	$109.80
Purchase #6	$225.89	6.506%	$240.5864	$240.59	$240.60	$240.60
Purchase #7	$107.25	5.443%	$113.0876	$113.09	$113.10	$113.10
7 purchase totals =	$1,079.28		$1,158.4704	$1,158.47	$1,158.50	$1,158.50