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	$6.76	10.356%	$7.4601	$7.46	$7.45	$7.50
Purchase #2	$183.69	7.234%	$196.9781	$196.98	$197.00	$197.00
Purchase #3	$95.59	13.426%	$108.4239	$108.42	$108.40	$108.40
Purchase #4	$85.28	10.234%	$94.0076	$94.01	$94.00	$94.00
Purchase #5	$250.54	3.503%	$259.3164	$259.32	$259.30	$259.30
Purchase #6	$170.35	10.463%	$188.1737	$188.17	$188.15	$188.20
Purchase #7	$197.40	6.844%	$210.9101	$210.91	$210.90	$210.90
7 purchase totals =	$989.61		$1,065.2699	$1,065.27	$1,065.20	$1,065.30