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	$98.82	9.758%	$108.4629	$108.46	$108.45	$108.50
Purchase #2	$91.56	9.533%	$100.2884	$100.29	$100.30	$100.30
Purchase #3	$185.77	6.572%	$197.9788	$197.98	$198.00	$198.00
Purchase #4	$72.97	8.802%	$79.3928	$79.39	$79.40	$79.40
Purchase #5	$227.55	12.710%	$256.4716	$256.47	$256.45	$256.50
Purchase #6	$115.76	7.493%	$124.4339	$124.43	$124.45	$124.40
Purchase #7	$64.30	5.346%	$67.7375	$67.74	$67.75	$67.70
7 purchase totals =	$856.73		$934.7659	$934.76	$934.80	$934.80