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	$148.79	12.719%	$167.7146	$167.71	$167.70	$167.70
Purchase #2	$80.82	11.493%	$90.1086	$90.11	$90.10	$90.10
Purchase #3	$54.92	4.158%	$57.2036	$57.20	$57.20	$57.20
Purchase #4	$149.91	7.328%	$160.8954	$160.90	$160.90	$160.90
Purchase #5	$31.47	13.396%	$35.6857	$35.69	$35.70	$35.70
Purchase #6	$196.55	8.133%	$212.5354	$212.54	$212.55	$212.50
Purchase #7	$55.98	10.248%	$61.7168	$61.72	$61.70	$61.70
7 purchase totals =	$718.44		$785.8601	$785.87	$785.85	$785.80