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	$120.78	8.544%	$131.0994	$131.10	$131.10	$131.10
Purchase #2	$155.91	5.344%	$164.2418	$164.24	$164.25	$164.20
Purchase #3	$250.33	4.586%	$261.8101	$261.81	$261.80	$261.80
Purchase #4	$174.49	3.567%	$180.7141	$180.71	$180.70	$180.70
Purchase #5	$85.73	4.837%	$89.8768	$89.88	$89.90	$89.90
Purchase #6	$185.51	3.375%	$191.771	$191.77	$191.75	$191.80
Purchase #7	$138.79	3.106%	$143.1008	$143.10	$143.10	$143.10
7 purchase totals =	$1,111.54		$1,162.6140	$1,162.61	$1,162.60	$1,162.60