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	$52.59	9.579%	$57.6276	$57.63	$57.65	$57.60
Purchase #2	$130.86	13.769%	$148.8781	$148.88	$148.90	$148.90
Purchase #3	$46.60	8.112%	$50.3802	$50.38	$50.40	$50.40
Purchase #4	$195.54	4.694%	$204.7186	$204.72	$204.70	$204.70
Purchase #5	$191.53	10.470%	$211.5832	$211.58	$211.60	$211.60
Purchase #6	$241.80	13.865%	$275.3256	$275.33	$275.35	$275.30
Purchase #7	$218.41	5.821%	$231.1236	$231.12	$231.10	$231.10
7 purchase totals =	$1,077.33		$1,179.6369	$1,179.64	$1,179.70	$1,179.60