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	$64.86	5.550%	$68.4597	$68.46	$68.45	$68.50
Purchase #2	$148.77	5.220%	$156.5358	$156.54	$156.55	$156.50
Purchase #3	$89.73	10.772%	$99.3957	$99.40	$99.40	$99.40
Purchase #4	$32.99	6.598%	$35.1667	$35.17	$35.15	$35.20
Purchase #5	$230.25	12.791%	$259.7013	$259.70	$259.70	$259.70
Purchase #6	$175.90	8.774%	$191.3335	$191.33	$191.35	$191.30
Purchase #7	$187.56	4.732%	$196.4353	$196.44	$196.45	$196.40
7 purchase totals =	$930.06		$1,007.0280	$1,007.04	$1,007.05	$1,007.00