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	$45.79	3.520%	$47.4018	$47.40	$47.40	$47.40
Purchase #2	$42.48	6.392%	$45.1953	$45.20	$45.20	$45.20
Purchase #3	$166.39	3.346%	$171.9574	$171.96	$171.95	$172.00
Purchase #4	$53.33	4.106%	$55.5197	$55.52	$55.50	$55.50
Purchase #5	$222.87	10.286%	$245.7944	$245.79	$245.80	$245.80
Purchase #6	$50.64	7.812%	$54.596	$54.60	$54.60	$54.60
Purchase #7	$147.59	10.199%	$162.6427	$162.64	$162.65	$162.60
7 purchase totals =	$729.09		$783.1073	$783.11	$783.10	$783.10