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	$185.25	5.171%	$194.8293	$194.83	$194.85	$194.80
Purchase #2	$85.34	8.809%	$92.8576	$92.86	$92.85	$92.90
Purchase #3	$173.85	9.391%	$190.1763	$190.18	$190.20	$190.20
Purchase #4	$209.33	9.563%	$229.3482	$229.35	$229.35	$229.30
Purchase #5	$97.31	13.173%	$110.1286	$110.13	$110.15	$110.10
Purchase #6	$227.50	5.618%	$240.281	$240.28	$240.30	$240.30
Purchase #7	$134.34	6.587%	$143.189	$143.19	$143.20	$143.20
7 purchase totals =	$1,112.92		$1,200.8100	$1,200.82	$1,200.90	$1,200.80