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	$9.73	4.266%	$10.1451	$10.15	$10.15	$10.10
Purchase #2	$87.71	13.512%	$99.5614	$99.56	$99.55	$99.60
Purchase #3	$78.28	4.373%	$81.7032	$81.70	$81.70	$81.70
Purchase #4	$173.58	6.656%	$185.1335	$185.13	$185.15	$185.10
Purchase #5	$171.75	6.401%	$182.7437	$182.74	$182.75	$182.70
Purchase #6	$210.46	6.740%	$224.645	$224.65	$224.65	$224.60
Purchase #7	$127.38	11.867%	$142.4962	$142.50	$142.50	$142.50
7 purchase totals =	$858.89		$926.4281	$926.43	$926.45	$926.30