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	$91.79	6.466%	$97.7251	$97.73	$97.75	$97.70
Purchase #2	$194.40	11.251%	$216.2719	$216.27	$216.25	$216.30
Purchase #3	$98.47	7.202%	$105.5618	$105.56	$105.55	$105.60
Purchase #4	$65.87	8.328%	$71.3557	$71.36	$71.35	$71.40
Purchase #5	$199.37	13.329%	$225.944	$225.94	$225.95	$225.90
Purchase #6	$135.83	12.215%	$152.4216	$152.42	$152.40	$152.40
Purchase #7	$199.55	13.688%	$226.8644	$226.86	$226.85	$226.90
7 purchase totals =	$985.28		$1,096.1445	$1,096.14	$1,096.10	$1,096.20