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	$211.55	9.584%	$231.825	$231.83	$231.85	$231.80
Purchase #2	$153.49	9.701%	$168.3801	$168.38	$168.40	$168.40
Purchase #3	$230.35	5.343%	$242.6576	$242.66	$242.65	$242.70
Purchase #4	$165.89	9.501%	$181.6512	$181.65	$181.65	$181.70
Purchase #5	$107.50	7.872%	$115.9624	$115.96	$115.95	$116.00
Purchase #6	$77.32	6.138%	$82.0659	$82.07	$82.05	$82.10
Purchase #7	$162.61	3.787%	$168.768	$168.77	$168.75	$168.80
7 purchase totals =	$1,108.71		$1,191.3102	$1,191.32	$1,191.30	$1,191.50