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	$101.61	12.718%	$114.5328	$114.53	$114.55	$114.50
Purchase #2	$135.86	4.200%	$141.5661	$141.57	$141.55	$141.60
Purchase #3	$145.90	9.186%	$159.3024	$159.30	$159.30	$159.30
Purchase #4	$94.69	11.678%	$105.7479	$105.75	$105.75	$105.70
Purchase #5	$34.84	6.495%	$37.1029	$37.10	$37.10	$37.10
Purchase #6	$91.75	8.407%	$99.4634	$99.46	$99.45	$99.50
Purchase #7	$31.46	7.609%	$33.8538	$33.85	$33.85	$33.90
7 purchase totals =	$636.11		$691.5693	$691.56	$691.55	$691.60