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	$236.91	5.626%	$250.2386	$250.24	$250.25	$250.20
Purchase #2	$101.92	13.452%	$115.6303	$115.63	$115.65	$115.60
Purchase #3	$140.32	4.332%	$146.3987	$146.40	$146.40	$146.40
Purchase #4	$222.37	3.125%	$229.3191	$229.32	$229.30	$229.30
Purchase #5	$65.42	10.133%	$72.049	$72.05	$72.05	$72.00
Purchase #6	$110.91	11.183%	$123.3131	$123.31	$123.30	$123.30
Purchase #7	$101.33	6.858%	$108.2792	$108.28	$108.30	$108.30
7 purchase totals =	$979.18		$1,045.2280	$1,045.23	$1,045.25	$1,045.10