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	$139.77	8.856%	$152.148	$152.15	$152.15	$152.10
Purchase #2	$29.39	13.573%	$33.3791	$33.38	$33.40	$33.40
Purchase #3	$236.60	8.305%	$256.2496	$256.25	$256.25	$256.20
Purchase #4	$183.62	7.628%	$197.6265	$197.63	$197.65	$197.60
Purchase #5	$114.92	13.399%	$130.3181	$130.32	$130.30	$130.30
Purchase #6	$159.88	7.358%	$171.644	$171.64	$171.65	$171.60
Purchase #7	$216.46	12.655%	$243.853	$243.85	$243.85	$243.90
7 purchase totals =	$1,080.64		$1,185.2183	$1,185.22	$1,185.25	$1,185.10