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	$228.59	5.395%	$240.9224	$240.92	$240.90	$240.90
Purchase #2	$78.53	13.440%	$89.0844	$89.08	$89.10	$89.10
Purchase #3	$223.71	7.781%	$241.1169	$241.12	$241.10	$241.10
Purchase #4	$154.56	10.733%	$171.1489	$171.15	$171.15	$171.10
Purchase #5	$147.83	12.789%	$166.736	$166.74	$166.75	$166.70
Purchase #6	$98.87	7.496%	$106.2813	$106.28	$106.30	$106.30
Purchase #7	$56.64	5.467%	$59.7365	$59.74	$59.75	$59.70
7 purchase totals =	$988.73		$1,075.0264	$1,075.03	$1,075.05	$1,074.90