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	$149.29	4.644%	$156.223	$156.22	$156.20	$156.20
Purchase #2	$204.27	13.501%	$231.8485	$231.85	$231.85	$231.80
Purchase #3	$221.41	7.685%	$238.4254	$238.43	$238.45	$238.40
Purchase #4	$236.68	3.737%	$245.5247	$245.52	$245.50	$245.50
Purchase #5	$191.57	13.476%	$217.386	$217.39	$217.40	$217.40
Purchase #6	$75.25	4.840%	$78.8921	$78.89	$78.90	$78.90
Purchase #7	$64.92	12.419%	$72.9824	$72.98	$73.00	$73.00
7 purchase totals =	$1,143.39		$1,241.2821	$1,241.28	$1,241.30	$1,241.20