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	$143.46	6.462%	$152.7304	$152.73	$152.75	$152.70
Purchase #2	$107.33	3.588%	$111.181	$111.18	$111.20	$111.20
Purchase #3	$82.27	8.285%	$89.0861	$89.09	$89.10	$89.10
Purchase #4	$144.61	3.800%	$150.1052	$150.11	$150.10	$150.10
Purchase #5	$171.25	11.637%	$191.1784	$191.18	$191.20	$191.20
Purchase #6	$219.88	12.565%	$247.5079	$247.51	$247.50	$247.50
Purchase #7	$82.28	11.272%	$91.5546	$91.55	$91.55	$91.60
7 purchase totals =	$951.08		$1,033.3436	$1,033.35	$1,033.40	$1,033.40