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	$37.76	9.743%	$41.439	$41.44	$41.45	$41.40
Purchase #2	$240.69	11.375%	$268.0685	$268.07	$268.05	$268.10
Purchase #3	$48.35	5.685%	$51.0987	$51.10	$51.10	$51.10
Purchase #4	$45.96	9.512%	$50.3317	$50.33	$50.35	$50.30
Purchase #5	$211.27	12.795%	$238.302	$238.30	$238.30	$238.30
Purchase #6	$144.56	11.300%	$160.8953	$160.90	$160.90	$160.90
Purchase #7	$185.45	11.202%	$206.2241	$206.22	$206.20	$206.20
7 purchase totals =	$914.04		$1,016.3593	$1,016.36	$1,016.35	$1,016.30