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	$98.62	7.580%	$106.0954	$106.10	$106.10	$106.10
Purchase #2	$51.29	4.300%	$53.4955	$53.50	$53.50	$53.50
Purchase #3	$196.25	10.349%	$216.5599	$216.56	$216.55	$216.60
Purchase #4	$248.26	7.333%	$266.4649	$266.46	$266.45	$266.50
Purchase #5	$78.88	13.366%	$89.4231	$89.42	$89.40	$89.40
Purchase #6	$12.64	9.804%	$13.8792	$13.88	$13.90	$13.90
Purchase #7	$225.79	6.491%	$240.446	$240.45	$240.45	$240.40
7 purchase totals =	$911.73		$986.3640	$986.37	$986.35	$986.40