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	$50.49	6.831%	$53.939	$53.94	$53.95	$53.90
Purchase #2	$148.39	12.810%	$167.3988	$167.40	$167.40	$167.40
Purchase #3	$80.82	11.612%	$90.2048	$90.20	$90.20	$90.20
Purchase #4	$31.39	4.238%	$32.7203	$32.72	$32.70	$32.70
Purchase #5	$73.32	7.495%	$78.8153	$78.82	$78.80	$78.80
Purchase #6	$138.90	9.530%	$152.1372	$152.14	$152.15	$152.10
Purchase #7	$183.65	12.861%	$207.2692	$207.27	$207.25	$207.30
7 purchase totals =	$706.96		$782.4846	$782.49	$782.45	$782.40