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	$97.66	6.388%	$103.8985	$103.90	$103.90	$103.90
Purchase #2	$99.78	6.543%	$106.3086	$106.31	$106.30	$106.30
Purchase #3	$5.73	3.501%	$5.9306	$5.93	$5.95	$5.90
Purchase #4	$104.74	5.419%	$110.4159	$110.42	$110.40	$110.40
Purchase #5	$78.66	4.863%	$82.4852	$82.49	$82.50	$82.50
Purchase #6	$196.40	11.842%	$219.6577	$219.66	$219.65	$219.70
Purchase #7	$161.41	5.646%	$170.5232	$170.52	$170.50	$170.50
7 purchase totals =	$744.38		$799.2197	$799.23	$799.20	$799.20