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	$73.93	5.554%	$78.0361	$78.04	$78.05	$78.00
Purchase #2	$82.33	13.109%	$93.1226	$93.12	$93.10	$93.10
Purchase #3	$55.51	11.253%	$61.7565	$61.76	$61.75	$61.80
Purchase #4	$237.37	5.427%	$250.2521	$250.25	$250.25	$250.30
Purchase #5	$205.70	12.369%	$231.143	$231.14	$231.15	$231.10
Purchase #6	$161.30	12.551%	$181.5448	$181.54	$181.55	$181.50
Purchase #7	$155.39	8.425%	$168.4816	$168.48	$168.50	$168.50
7 purchase totals =	$971.53		$1,064.3367	$1,064.33	$1,064.35	$1,064.30