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	$140.52	7.194%	$150.629	$150.63	$150.65	$150.60
Purchase #2	$80.78	7.174%	$86.5752	$86.58	$86.60	$86.60
Purchase #3	$155.94	8.447%	$169.1123	$169.11	$169.10	$169.10
Purchase #4	$50.74	12.300%	$56.981	$56.98	$57.00	$57.00
Purchase #5	$162.72	5.279%	$171.31	$171.31	$171.30	$171.30
Purchase #6	$250.68	10.153%	$276.1315	$276.13	$276.15	$276.10
Purchase #7	$96.81	11.270%	$107.7205	$107.72	$107.70	$107.70
7 purchase totals =	$938.19		$1,018.4595	$1,018.46	$1,018.50	$1,018.40