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	$159.78	12.793%	$180.2207	$180.22	$180.20	$180.20
Purchase #2	$179.31	5.311%	$188.8332	$188.83	$188.85	$188.80
Purchase #3	$178.87	9.658%	$196.1453	$196.15	$196.15	$196.10
Purchase #4	$100.97	4.675%	$105.6903	$105.69	$105.70	$105.70
Purchase #5	$93.42	10.546%	$103.2721	$103.27	$103.25	$103.30
Purchase #6	$250.66	7.555%	$269.5974	$269.60	$269.60	$269.60
Purchase #7	$145.38	4.469%	$151.877	$151.88	$151.90	$151.90
7 purchase totals =	$1,108.39		$1,195.6360	$1,195.64	$1,195.65	$1,195.60