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	$46.64	11.682%	$52.0885	$52.09	$52.10	$52.10
Purchase #2	$61.76	6.428%	$65.7299	$65.73	$65.75	$65.70
Purchase #3	$180.30	9.772%	$197.9189	$197.92	$197.90	$197.90
Purchase #4	$192.44	7.501%	$206.8749	$206.87	$206.85	$206.90
Purchase #5	$153.48	7.114%	$164.3986	$164.40	$164.40	$164.40
Purchase #6	$143.85	4.654%	$150.5448	$150.54	$150.55	$150.50
Purchase #7	$238.25	4.627%	$249.2738	$249.27	$249.25	$249.30
7 purchase totals =	$1,016.72		$1,086.8294	$1,086.82	$1,086.80	$1,086.80