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	$181.98	12.218%	$204.2143	$204.21	$204.20	$204.20
Purchase #2	$191.50	5.181%	$201.4216	$201.42	$201.40	$201.40
Purchase #3	$105.69	3.250%	$109.1249	$109.12	$109.10	$109.10
Purchase #4	$185.51	6.809%	$198.1414	$198.14	$198.15	$198.10
Purchase #5	$142.63	5.761%	$150.8469	$150.85	$150.85	$150.80
Purchase #6	$43.59	4.740%	$45.6562	$45.66	$45.65	$45.70
Purchase #7	$196.80	8.773%	$214.0653	$214.07	$214.05	$214.10
7 purchase totals =	$1,047.70		$1,123.4706	$1,123.47	$1,123.40	$1,123.40