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	$50.97	4.571%	$53.2998	$53.30	$53.30	$53.30
Purchase #2	$210.53	5.500%	$222.1092	$222.11	$222.10	$222.10
Purchase #3	$238.83	10.576%	$264.0887	$264.09	$264.10	$264.10
Purchase #4	$35.79	5.798%	$37.8651	$37.87	$37.85	$37.90
Purchase #5	$57.83	3.829%	$60.0443	$60.04	$60.05	$60.00
Purchase #6	$216.41	10.645%	$239.4468	$239.45	$239.45	$239.40
Purchase #7	$199.46	10.563%	$220.529	$220.53	$220.55	$220.50
7 purchase totals =	$1,009.82		$1,097.3829	$1,097.39	$1,097.40	$1,097.30