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	$225.58	7.703%	$242.9564	$242.96	$242.95	$243.00
Purchase #2	$81.64	9.607%	$89.4832	$89.48	$89.50	$89.50
Purchase #3	$96.84	9.349%	$105.8936	$105.89	$105.90	$105.90
Purchase #4	$171.75	7.844%	$185.2221	$185.22	$185.20	$185.20
Purchase #5	$199.66	4.707%	$209.058	$209.06	$209.05	$209.10
Purchase #6	$117.32	6.307%	$124.7194	$124.72	$124.70	$124.70
Purchase #7	$122.27	7.190%	$131.0612	$131.06	$131.05	$131.10
7 purchase totals =	$1,015.06		$1,088.3939	$1,088.39	$1,088.35	$1,088.50