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	$201.54	10.872%	$223.4514	$223.45	$223.45	$223.50
Purchase #2	$221.69	9.234%	$242.1609	$242.16	$242.15	$242.20
Purchase #3	$153.55	11.675%	$171.477	$171.48	$171.50	$171.50
Purchase #4	$46.73	6.129%	$49.5941	$49.59	$49.60	$49.60
Purchase #5	$142.60	9.788%	$156.5577	$156.56	$156.55	$156.60
Purchase #6	$208.90	5.217%	$219.7983	$219.80	$219.80	$219.80
Purchase #7	$58.81	11.743%	$65.7161	$65.72	$65.70	$65.70
7 purchase totals =	$1,033.82		$1,128.7555	$1,128.76	$1,128.75	$1,128.90