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	$71.54	8.104%	$77.3376	$77.34	$77.35	$77.30
Purchase #2	$234.74	12.758%	$264.6881	$264.69	$264.70	$264.70
Purchase #3	$209.43	9.502%	$229.33	$229.33	$229.35	$229.30
Purchase #4	$52.86	12.706%	$59.5764	$59.58	$59.60	$59.60
Purchase #5	$126.96	5.630%	$134.1078	$134.11	$134.10	$134.10
Purchase #6	$63.69	5.637%	$67.2802	$67.28	$67.30	$67.30
Purchase #7	$219.80	8.120%	$237.6478	$237.65	$237.65	$237.60
7 purchase totals =	$979.02		$1,069.9679	$1,069.98	$1,070.05	$1,069.90