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	$141.57	6.848%	$151.2647	$151.26	$151.25	$151.30
Purchase #2	$89.38	11.376%	$99.5479	$99.55	$99.55	$99.50
Purchase #3	$237.64	10.442%	$262.4544	$262.45	$262.45	$262.50
Purchase #4	$170.61	10.279%	$188.147	$188.15	$188.15	$188.10
Purchase #5	$84.50	4.189%	$88.0397	$88.04	$88.05	$88.00
Purchase #6	$185.45	5.337%	$195.3475	$195.35	$195.35	$195.30
Purchase #7	$96.80	10.372%	$106.8401	$106.84	$106.85	$106.80
7 purchase totals =	$1,005.95		$1,091.6413	$1,091.64	$1,091.65	$1,091.50