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	$68.74	4.520%	$71.847	$71.85	$71.85	$71.80
Purchase #2	$73.46	6.305%	$78.0917	$78.09	$78.10	$78.10
Purchase #3	$154.84	11.521%	$172.6791	$172.68	$172.70	$172.70
Purchase #4	$121.91	4.428%	$127.3082	$127.31	$127.30	$127.30
Purchase #5	$171.55	13.392%	$194.524	$194.52	$194.50	$194.50
Purchase #6	$128.64	13.153%	$145.56	$145.56	$145.55	$145.60
Purchase #7	$191.46	9.791%	$210.2058	$210.21	$210.20	$210.20
7 purchase totals =	$910.60		$1,000.2158	$1,000.22	$1,000.20	$1,000.20