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	$209.65	10.132%	$230.8917	$230.89	$230.90	$230.90
Purchase #2	$51.53	13.546%	$58.5103	$58.51	$58.50	$58.50
Purchase #3	$86.40	5.637%	$91.2704	$91.27	$91.25	$91.30
Purchase #4	$182.35	3.395%	$188.5408	$188.54	$188.55	$188.50
Purchase #5	$131.76	8.717%	$143.2455	$143.25	$143.25	$143.20
Purchase #6	$101.96	10.850%	$113.0227	$113.02	$113.00	$113.00
Purchase #7	$178.49	8.722%	$194.0579	$194.06	$194.05	$194.10
7 purchase totals =	$942.14		$1,019.5393	$1,019.54	$1,019.50	$1,019.50