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	$234.98	7.445%	$252.4743	$252.47	$252.45	$252.50
Purchase #2	$168.49	9.173%	$183.9456	$183.95	$183.95	$183.90
Purchase #3	$38.92	12.850%	$43.9212	$43.92	$43.90	$43.90
Purchase #4	$160.27	5.121%	$168.4774	$168.48	$168.50	$168.50
Purchase #5	$222.69	7.343%	$239.0421	$239.04	$239.05	$239.00
Purchase #6	$128.74	10.503%	$142.2616	$142.26	$142.25	$142.30
Purchase #7	$48.42	9.656%	$53.0954	$53.10	$53.10	$53.10
7 purchase totals =	$1,002.51		$1,083.2176	$1,083.22	$1,083.20	$1,083.20