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	$210.49	7.159%	$225.559	$225.56	$225.55	$225.60
Purchase #2	$162.98	13.666%	$185.2528	$185.25	$185.25	$185.30
Purchase #3	$175.47	10.700%	$194.2453	$194.25	$194.25	$194.20
Purchase #4	$115.52	10.473%	$127.6184	$127.62	$127.60	$127.60
Purchase #5	$77.84	7.379%	$83.5838	$83.58	$83.60	$83.60
Purchase #6	$160.31	7.347%	$172.088	$172.09	$172.10	$172.10
Purchase #7	$141.50	12.165%	$158.7135	$158.71	$158.70	$158.70
7 purchase totals =	$1,044.11		$1,147.0608	$1,147.06	$1,147.05	$1,147.10