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	$184.29	12.349%	$207.048	$207.05	$207.05	$207.00
Purchase #2	$83.76	7.835%	$90.3226	$90.32	$90.30	$90.30
Purchase #3	$112.37	9.516%	$123.0631	$123.06	$123.05	$123.10
Purchase #4	$205.83	8.717%	$223.7722	$223.77	$223.75	$223.80
Purchase #5	$65.96	10.538%	$72.9109	$72.91	$72.90	$72.90
Purchase #6	$56.37	8.818%	$61.3407	$61.34	$61.35	$61.30
Purchase #7	$235.75	12.636%	$265.5394	$265.54	$265.55	$265.50
7 purchase totals =	$944.33		$1,043.9969	$1,043.99	$1,043.95	$1,043.90