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	$45.76	6.711%	$48.831	$48.83	$48.85	$48.80
Purchase #2	$33.53	5.505%	$35.3758	$35.38	$35.40	$35.40
Purchase #3	$222.73	3.168%	$229.7861	$229.79	$229.80	$229.80
Purchase #4	$203.91	6.505%	$217.1743	$217.17	$217.15	$217.20
Purchase #5	$108.97	7.760%	$117.4261	$117.43	$117.45	$117.40
Purchase #6	$161.45	11.577%	$180.1411	$180.14	$180.15	$180.10
Purchase #7	$156.55	9.435%	$171.3205	$171.32	$171.30	$171.30
7 purchase totals =	$932.90		$1,000.0549	$1,000.06	$1,000.10	$1,000.00