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	$181.87	13.562%	$206.5352	$206.54	$206.55	$206.50
Purchase #2	$42.75	4.423%	$44.6408	$44.64	$44.65	$44.60
Purchase #3	$88.30	4.134%	$91.9503	$91.95	$91.95	$92.00
Purchase #4	$188.40	4.430%	$196.7461	$196.75	$196.75	$196.70
Purchase #5	$116.41	9.390%	$127.3409	$127.34	$127.35	$127.30
Purchase #6	$41.64	4.268%	$43.4172	$43.42	$43.40	$43.40
Purchase #7	$11.75	13.451%	$13.3305	$13.33	$13.35	$13.30
7 purchase totals =	$671.12		$723.9610	$723.97	$724.00	$723.80