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	$165.55	5.242%	$174.2281	$174.23	$174.25	$174.20
Purchase #2	$57.94	6.869%	$61.9199	$61.92	$61.90	$61.90
Purchase #3	$101.30	11.288%	$112.7347	$112.73	$112.75	$112.70
Purchase #4	$88.46	11.263%	$98.4232	$98.42	$98.40	$98.40
Purchase #5	$90.83	5.225%	$95.5759	$95.58	$95.60	$95.60
Purchase #6	$110.78	4.738%	$116.0288	$116.03	$116.05	$116.00
Purchase #7	$143.68	10.407%	$158.6328	$158.63	$158.65	$158.60
7 purchase totals =	$758.54		$817.5434	$817.54	$817.60	$817.40