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	$235.54	4.789%	$246.82	$246.82	$246.80	$246.80
Purchase #2	$105.52	10.436%	$116.5321	$116.53	$116.55	$116.50
Purchase #3	$112.64	11.458%	$125.5463	$125.55	$125.55	$125.50
Purchase #4	$59.35	4.360%	$61.9377	$61.94	$61.95	$61.90
Purchase #5	$162.46	13.354%	$184.1549	$184.15	$184.15	$184.20
Purchase #6	$183.98	11.524%	$205.1819	$205.18	$205.20	$205.20
Purchase #7	$125.34	13.400%	$142.1356	$142.14	$142.15	$142.10
7 purchase totals =	$984.83		$1,082.3085	$1,082.31	$1,082.35	$1,082.20