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	$124.91	4.144%	$130.0863	$130.09	$130.10	$130.10
Purchase #2	$211.56	5.104%	$222.358	$222.36	$222.35	$222.40
Purchase #3	$9.64	12.251%	$10.821	$10.82	$10.80	$10.80
Purchase #4	$73.66	11.562%	$82.1766	$82.18	$82.20	$82.20
Purchase #5	$37.53	11.520%	$41.8535	$41.85	$41.85	$41.90
Purchase #6	$225.92	13.869%	$257.2528	$257.25	$257.25	$257.30
Purchase #7	$239.25	9.725%	$262.5171	$262.52	$262.50	$262.50
7 purchase totals =	$922.47		$1,007.0653	$1,007.07	$1,007.05	$1,007.20