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	$188.72	4.365%	$196.9576	$196.96	$196.95	$197.00
Purchase #2	$111.30	8.872%	$121.1745	$121.17	$121.15	$121.20
Purchase #3	$133.87	11.245%	$148.9237	$148.92	$148.90	$148.90
Purchase #4	$237.81	5.682%	$251.3224	$251.32	$251.30	$251.30
Purchase #5	$97.80	11.843%	$109.3825	$109.38	$109.40	$109.40
Purchase #6	$77.61	6.729%	$82.8324	$82.83	$82.85	$82.80
Purchase #7	$232.86	6.799%	$248.6922	$248.69	$248.70	$248.70
7 purchase totals =	$1,079.97		$1,159.2853	$1,159.27	$1,159.25	$1,159.30