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	$48.36	10.245%	$53.3145	$53.31	$53.30	$53.30
Purchase #2	$172.92	7.182%	$185.3391	$185.34	$185.35	$185.30
Purchase #3	$178.60	4.331%	$186.3352	$186.34	$186.35	$186.30
Purchase #4	$148.88	13.529%	$169.022	$169.02	$169.00	$169.00
Purchase #5	$144.69	3.143%	$149.2376	$149.24	$149.25	$149.20
Purchase #6	$78.65	12.285%	$88.3122	$88.31	$88.30	$88.30
Purchase #7	$94.55	6.178%	$100.3913	$100.39	$100.40	$100.40
7 purchase totals =	$866.65		$931.9519	$931.95	$931.95	$931.80