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	$201.69	4.118%	$209.9956	$210.00	$210.00	$210.00
Purchase #2	$148.87	5.219%	$156.6395	$156.64	$156.65	$156.60
Purchase #3	$175.83	7.222%	$188.5284	$188.53	$188.55	$188.50
Purchase #4	$202.40	3.672%	$209.8321	$209.83	$209.85	$209.80
Purchase #5	$51.48	11.335%	$57.3153	$57.32	$57.30	$57.30
Purchase #6	$116.36	5.870%	$123.1903	$123.19	$123.20	$123.20
Purchase #7	$107.63	7.517%	$115.7205	$115.72	$115.70	$115.70
7 purchase totals =	$1,004.26		$1,061.2217	$1,061.23	$1,061.25	$1,061.10