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	$97.44	5.331%	$102.6345	$102.63	$102.65	$102.60
Purchase #2	$135.75	11.498%	$151.3585	$151.36	$151.35	$151.40
Purchase #3	$146.70	10.735%	$162.4482	$162.45	$162.45	$162.40
Purchase #4	$26.34	6.140%	$27.9573	$27.96	$27.95	$28.00
Purchase #5	$172.28	8.326%	$186.624	$186.62	$186.60	$186.60
Purchase #6	$144.98	12.336%	$162.8647	$162.86	$162.85	$162.90
Purchase #7	$209.46	6.192%	$222.4298	$222.43	$222.45	$222.40
7 purchase totals =	$932.95		$1,016.3170	$1,016.31	$1,016.30	$1,016.30