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	$173.76	6.450%	$184.9675	$184.97	$184.95	$185.00
Purchase #2	$64.42	5.468%	$67.9425	$67.94	$67.95	$67.90
Purchase #3	$165.56	13.300%	$187.5795	$187.58	$187.60	$187.60
Purchase #4	$94.93	10.669%	$105.0581	$105.06	$105.05	$105.10
Purchase #5	$221.30	3.613%	$229.2956	$229.30	$229.30	$229.30
Purchase #6	$132.68	13.137%	$150.1102	$150.11	$150.10	$150.10
Purchase #7	$132.60	7.389%	$142.3978	$142.40	$142.40	$142.40
7 purchase totals =	$985.25		$1,067.3512	$1,067.36	$1,067.35	$1,067.40