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	$67.74	6.325%	$72.0246	$72.02	$72.00	$72.00
Purchase #2	$91.62	10.123%	$100.8947	$100.89	$100.90	$100.90
Purchase #3	$27.96	10.404%	$30.869	$30.87	$30.85	$30.90
Purchase #4	$39.31	7.621%	$42.3058	$42.31	$42.30	$42.30
Purchase #5	$162.94	7.128%	$174.5544	$174.55	$174.55	$174.60
Purchase #6	$211.67	10.382%	$233.6456	$233.65	$233.65	$233.60
Purchase #7	$29.50	3.367%	$30.4933	$30.49	$30.50	$30.50
7 purchase totals =	$630.74		$684.7874	$684.78	$684.75	$684.80