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	$196.82	6.479%	$209.572	$209.57	$209.55	$209.60
Purchase #2	$129.33	13.304%	$146.5361	$146.54	$146.55	$146.50
Purchase #3	$61.84	13.481%	$70.1767	$70.18	$70.20	$70.20
Purchase #4	$99.79	9.654%	$109.4237	$109.42	$109.40	$109.40
Purchase #5	$170.33	3.333%	$176.0071	$176.01	$176.00	$176.00
Purchase #6	$148.70	11.341%	$165.5641	$165.56	$165.55	$165.60
Purchase #7	$209.49	9.809%	$230.0389	$230.04	$230.05	$230.00
7 purchase totals =	$1,016.30		$1,107.3186	$1,107.32	$1,107.30	$1,107.30