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	$168.36	8.341%	$182.4029	$182.40	$182.40	$182.40
Purchase #2	$144.52	12.546%	$162.6515	$162.65	$162.65	$162.70
Purchase #3	$61.56	10.634%	$68.1063	$68.11	$68.10	$68.10
Purchase #4	$104.89	6.574%	$111.7855	$111.79	$111.80	$111.80
Purchase #5	$118.93	8.398%	$128.9177	$128.92	$128.90	$128.90
Purchase #6	$162.65	11.429%	$181.2393	$181.24	$181.25	$181.20
Purchase #7	$164.95	12.329%	$185.2867	$185.29	$185.30	$185.30
7 purchase totals =	$925.86		$1,020.3899	$1,020.40	$1,020.40	$1,020.40