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	$134.63	13.557%	$152.8818	$152.88	$152.90	$152.90
Purchase #2	$240.93	3.824%	$250.1432	$250.14	$250.15	$250.10
Purchase #3	$40.88	11.170%	$45.4463	$45.45	$45.45	$45.40
Purchase #4	$219.37	4.473%	$229.1824	$229.18	$229.20	$229.20
Purchase #5	$61.56	10.297%	$67.8988	$67.90	$67.90	$67.90
Purchase #6	$121.31	13.815%	$138.069	$138.07	$138.05	$138.10
Purchase #7	$168.73	8.843%	$183.6508	$183.65	$183.65	$183.70
7 purchase totals =	$987.41		$1,067.2723	$1,067.27	$1,067.30	$1,067.30