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	$219.36	3.374%	$226.7612	$226.76	$226.75	$226.80
Purchase #2	$33.48	6.541%	$35.6699	$35.67	$35.65	$35.70
Purchase #3	$127.85	3.160%	$131.8901	$131.89	$131.90	$131.90
Purchase #4	$156.98	3.559%	$162.5669	$162.57	$162.55	$162.60
Purchase #5	$187.63	6.428%	$199.6909	$199.69	$199.70	$199.70
Purchase #6	$123.81	4.675%	$129.5981	$129.60	$129.60	$129.60
Purchase #7	$172.71	7.233%	$185.2021	$185.20	$185.20	$185.20
7 purchase totals =	$1,021.82		$1,071.3792	$1,071.38	$1,071.35	$1,071.50