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	$73.76	9.486%	$80.7569	$80.76	$80.75	$80.80
Purchase #2	$29.80	8.258%	$32.2609	$32.26	$32.25	$32.30
Purchase #3	$230.46	5.570%	$243.2966	$243.30	$243.30	$243.30
Purchase #4	$191.53	11.387%	$213.3395	$213.34	$213.35	$213.30
Purchase #5	$123.71	13.387%	$140.2711	$140.27	$140.25	$140.30
Purchase #6	$153.88	8.566%	$167.0614	$167.06	$167.05	$167.10
Purchase #7	$152.28	11.172%	$169.2927	$169.29	$169.30	$169.30
7 purchase totals =	$955.42		$1,046.2791	$1,046.28	$1,046.25	$1,046.40