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	$174.47	6.271%	$185.411	$185.41	$185.40	$185.40
Purchase #2	$191.35	8.651%	$207.9037	$207.90	$207.90	$207.90
Purchase #3	$231.91	3.530%	$240.0964	$240.10	$240.10	$240.10
Purchase #4	$132.93	3.619%	$137.7407	$137.74	$137.75	$137.70
Purchase #5	$150.53	6.468%	$160.2663	$160.27	$160.25	$160.30
Purchase #6	$183.47	9.314%	$200.5584	$200.56	$200.55	$200.60
Purchase #7	$59.81	7.423%	$64.2497	$64.25	$64.25	$64.20
7 purchase totals =	$1,124.47		$1,196.2262	$1,196.23	$1,196.20	$1,196.20