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	$134.84	4.657%	$141.1195	$141.12	$141.10	$141.10
Purchase #2	$150.43	11.442%	$167.6422	$167.64	$167.65	$167.60
Purchase #3	$168.76	13.640%	$191.7789	$191.78	$191.80	$191.80
Purchase #4	$18.38	12.158%	$20.6146	$20.61	$20.60	$20.60
Purchase #5	$53.59	11.335%	$59.6644	$59.66	$59.65	$59.70
Purchase #6	$95.61	12.194%	$107.2687	$107.27	$107.25	$107.30
Purchase #7	$125.90	5.819%	$133.2261	$133.23	$133.25	$133.20
7 purchase totals =	$747.51		$821.3144	$821.31	$821.30	$821.30