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	$134.29	7.285%	$144.073	$144.07	$144.05	$144.10
Purchase #2	$94.55	6.573%	$100.7648	$100.76	$100.75	$100.80
Purchase #3	$151.70	7.221%	$162.6543	$162.65	$162.65	$162.70
Purchase #4	$66.77	6.200%	$70.9097	$70.91	$70.90	$70.90
Purchase #5	$120.96	11.459%	$134.8208	$134.82	$134.80	$134.80
Purchase #6	$34.32	11.535%	$38.2788	$38.28	$38.30	$38.30
Purchase #7	$123.52	7.133%	$132.3307	$132.33	$132.35	$132.30
7 purchase totals =	$726.11		$783.8321	$783.82	$783.80	$783.90