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	$177.95	10.253%	$196.1952	$196.20	$196.20	$196.20
Purchase #2	$167.79	13.190%	$189.9215	$189.92	$189.90	$189.90
Purchase #3	$178.87	11.256%	$199.0036	$199.00	$199.00	$199.00
Purchase #4	$61.46	9.114%	$67.0615	$67.06	$67.05	$67.10
Purchase #5	$124.28	7.240%	$133.2779	$133.28	$133.30	$133.30
Purchase #6	$215.53	6.291%	$229.089	$229.09	$229.10	$229.10
Purchase #7	$54.97	4.285%	$57.3255	$57.33	$57.35	$57.30
7 purchase totals =	$980.85		$1,071.8742	$1,071.88	$1,071.90	$1,071.90