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	$50.78	6.449%	$54.0548	$54.05	$54.05	$54.10
Purchase #2	$37.93	8.735%	$41.2432	$41.24	$41.25	$41.20
Purchase #3	$58.30	5.420%	$61.4599	$61.46	$61.45	$61.50
Purchase #4	$85.82	6.569%	$91.4575	$91.46	$91.45	$91.50
Purchase #5	$25.96	10.786%	$28.76	$28.76	$28.75	$28.80
Purchase #6	$106.33	9.132%	$116.0401	$116.04	$116.05	$116.00
Purchase #7	$47.87	11.620%	$53.4325	$53.43	$53.45	$53.40
7 purchase totals =	$412.99		$446.4480	$446.44	$446.45	$446.50