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	$73.36	6.690%	$78.2678	$78.27	$78.25	$78.30
Purchase #2	$196.50	7.403%	$211.0469	$211.05	$211.05	$211.00
Purchase #3	$178.29	9.790%	$195.7446	$195.74	$195.75	$195.70
Purchase #4	$207.39	12.574%	$233.4672	$233.47	$233.45	$233.50
Purchase #5	$133.54	8.477%	$144.8602	$144.86	$144.85	$144.90
Purchase #6	$56.37	8.741%	$61.2973	$61.30	$61.30	$61.30
Purchase #7	$159.79	6.340%	$169.9207	$169.92	$169.90	$169.90
7 purchase totals =	$1,005.24		$1,094.6047	$1,094.61	$1,094.55	$1,094.60