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	$221.49	5.359%	$233.3596	$233.36	$233.35	$233.40
Purchase #2	$186.38	5.247%	$196.1594	$196.16	$196.15	$196.20
Purchase #3	$245.98	5.592%	$259.7352	$259.74	$259.75	$259.70
Purchase #4	$189.97	3.347%	$196.3283	$196.33	$196.35	$196.30
Purchase #5	$155.85	13.110%	$176.2819	$176.28	$176.30	$176.30
Purchase #6	$96.71	6.246%	$102.7505	$102.75	$102.75	$102.80
Purchase #7	$18.39	11.370%	$20.4809	$20.48	$20.50	$20.50
7 purchase totals =	$1,114.77		$1,185.0958	$1,185.10	$1,185.15	$1,185.20