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	$190.98	10.229%	$210.5153	$210.52	$210.50	$210.50
Purchase #2	$43.47	11.407%	$48.4286	$48.43	$48.45	$48.40
Purchase #3	$228.72	8.844%	$248.948	$248.95	$248.95	$248.90
Purchase #4	$131.61	6.585%	$140.2765	$140.28	$140.30	$140.30
Purchase #5	$36.36	11.433%	$40.517	$40.52	$40.50	$40.50
Purchase #6	$56.72	10.277%	$62.5491	$62.55	$62.55	$62.50
Purchase #7	$91.61	5.551%	$96.6953	$96.70	$96.70	$96.70
7 purchase totals =	$779.47		$847.9298	$847.95	$847.95	$847.80