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	$215.25	3.814%	$223.4596	$223.46	$223.45	$223.50
Purchase #2	$247.33	13.333%	$280.3065	$280.31	$280.30	$280.30
Purchase #3	$64.74	10.656%	$71.6387	$71.64	$71.65	$71.60
Purchase #4	$150.61	10.405%	$166.281	$166.28	$166.30	$166.30
Purchase #5	$70.66	3.574%	$73.1854	$73.19	$73.20	$73.20
Purchase #6	$59.56	12.423%	$66.9591	$66.96	$66.95	$67.00
Purchase #7	$41.81	3.669%	$43.344	$43.34	$43.35	$43.30
7 purchase totals =	$849.96		$925.1743	$925.18	$925.20	$925.20