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	$148.31	7.638%	$159.6379	$159.64	$159.65	$159.60
Purchase #2	$104.69	5.298%	$110.2365	$110.24	$110.25	$110.20
Purchase #3	$64.98	8.683%	$70.6222	$70.62	$70.60	$70.60
Purchase #4	$144.50	10.459%	$159.6133	$159.61	$159.60	$159.60
Purchase #5	$130.75	8.785%	$142.2364	$142.24	$142.25	$142.20
Purchase #6	$229.87	6.740%	$245.3632	$245.36	$245.35	$245.40
Purchase #7	$120.36	6.162%	$127.7766	$127.78	$127.80	$127.80
7 purchase totals =	$943.46		$1,015.4861	$1,015.49	$1,015.50	$1,015.40