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	$94.77	5.329%	$99.8203	$99.82	$99.80	$99.80
Purchase #2	$96.78	13.410%	$109.7582	$109.76	$109.75	$109.80
Purchase #3	$116.88	11.717%	$130.5748	$130.57	$130.55	$130.60
Purchase #4	$174.43	10.346%	$192.4765	$192.48	$192.50	$192.50
Purchase #5	$54.96	4.580%	$57.4772	$57.48	$57.50	$57.50
Purchase #6	$42.37	11.121%	$47.082	$47.08	$47.10	$47.10
Purchase #7	$61.79	13.144%	$69.9117	$69.91	$69.90	$69.90
7 purchase totals =	$641.98		$707.1007	$707.10	$707.10	$707.20