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	$193.56	11.208%	$215.2542	$215.25	$215.25	$215.30
Purchase #2	$161.48	6.796%	$172.4542	$172.45	$172.45	$172.50
Purchase #3	$165.76	11.411%	$184.6749	$184.67	$184.65	$184.70
Purchase #4	$32.43	8.273%	$35.1129	$35.11	$35.10	$35.10
Purchase #5	$75.82	12.501%	$85.2983	$85.30	$85.30	$85.30
Purchase #6	$29.69	6.784%	$31.7042	$31.70	$31.70	$31.70
Purchase #7	$92.63	6.649%	$98.789	$98.79	$98.80	$98.80
7 purchase totals =	$751.37		$823.2877	$823.27	$823.25	$823.40