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	$185.32	6.804%	$197.9292	$197.93	$197.95	$197.90
Purchase #2	$161.51	12.326%	$181.4177	$181.42	$181.40	$181.40
Purchase #3	$57.82	11.657%	$64.5601	$64.56	$64.55	$64.60
Purchase #4	$170.50	13.850%	$194.1143	$194.11	$194.10	$194.10
Purchase #5	$192.65	12.841%	$217.3882	$217.39	$217.40	$217.40
Purchase #6	$133.35	9.204%	$145.6235	$145.62	$145.60	$145.60
Purchase #7	$55.27	7.204%	$59.2517	$59.25	$59.25	$59.30
7 purchase totals =	$956.42		$1,060.2847	$1,060.28	$1,060.25	$1,060.30