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	$110.59	3.843%	$114.84	$114.84	$114.85	$114.80
Purchase #2	$53.36	12.111%	$59.8224	$59.82	$59.80	$59.80
Purchase #3	$143.59	3.120%	$148.07	$148.07	$148.05	$148.10
Purchase #4	$240.29	3.258%	$248.1186	$248.12	$248.10	$248.10
Purchase #5	$249.76	11.308%	$278.0029	$278.00	$278.00	$278.00
Purchase #6	$99.31	13.628%	$112.844	$112.84	$112.85	$112.80
Purchase #7	$42.73	13.774%	$48.6156	$48.62	$48.60	$48.60
7 purchase totals =	$939.63		$1,010.3135	$1,010.31	$1,010.25	$1,010.20