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	$198.73	7.407%	$213.4499	$213.45	$213.45	$213.40
Purchase #2	$55.25	13.423%	$62.6662	$62.67	$62.65	$62.70
Purchase #3	$134.32	6.121%	$142.5417	$142.54	$142.55	$142.50
Purchase #4	$37.36	11.520%	$41.6639	$41.66	$41.65	$41.70
Purchase #5	$32.64	11.534%	$36.4047	$36.40	$36.40	$36.40
Purchase #6	$72.88	7.637%	$78.4458	$78.45	$78.45	$78.40
Purchase #7	$187.29	12.191%	$210.1225	$210.12	$210.10	$210.10
7 purchase totals =	$718.47		$785.2947	$785.29	$785.25	$785.20