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	$147.34	5.508%	$155.4555	$155.46	$155.45	$155.50
Purchase #2	$18.80	9.295%	$20.5475	$20.55	$20.55	$20.50
Purchase #3	$173.95	10.282%	$191.8355	$191.84	$191.85	$191.80
Purchase #4	$95.61	12.395%	$107.4609	$107.46	$107.45	$107.50
Purchase #5	$249.36	4.168%	$259.7533	$259.75	$259.75	$259.80
Purchase #6	$151.69	10.302%	$167.3171	$167.32	$167.30	$167.30
Purchase #7	$229.45	4.821%	$240.5118	$240.51	$240.50	$240.50
7 purchase totals =	$1,066.20		$1,142.8816	$1,142.89	$1,142.85	$1,142.90