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	$90.53	6.378%	$96.304	$96.30	$96.30	$96.30
Purchase #2	$204.77	8.591%	$222.3618	$222.36	$222.35	$222.40
Purchase #3	$90.93	13.839%	$103.5138	$103.51	$103.50	$103.50
Purchase #4	$76.71	7.791%	$82.6865	$82.69	$82.70	$82.70
Purchase #5	$222.66	3.154%	$229.6827	$229.68	$229.70	$229.70
Purchase #6	$93.51	3.185%	$96.4883	$96.49	$96.50	$96.50
Purchase #7	$211.27	6.297%	$224.5737	$224.57	$224.55	$224.60
7 purchase totals =	$990.38		$1,055.6108	$1,055.60	$1,055.60	$1,055.70