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	$44.29	7.507%	$47.6149	$47.61	$47.60	$47.60
Purchase #2	$56.61	11.846%	$63.316	$63.32	$63.30	$63.30
Purchase #3	$229.48	9.572%	$251.4458	$251.45	$251.45	$251.40
Purchase #4	$98.31	7.653%	$105.8337	$105.83	$105.85	$105.80
Purchase #5	$144.32	10.275%	$159.1489	$159.15	$159.15	$159.10
Purchase #6	$51.63	10.588%	$57.0966	$57.10	$57.10	$57.10
Purchase #7	$122.96	4.221%	$128.1501	$128.15	$128.15	$128.20
7 purchase totals =	$747.60		$812.6060	$812.61	$812.60	$812.50