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	$241.90	11.433%	$269.5564	$269.56	$269.55	$269.60
Purchase #2	$191.68	4.525%	$200.3535	$200.35	$200.35	$200.40
Purchase #3	$61.42	5.502%	$64.7993	$64.80	$64.80	$64.80
Purchase #4	$167.91	6.432%	$178.71	$178.71	$178.70	$178.70
Purchase #5	$164.51	11.194%	$182.9252	$182.93	$182.95	$182.90
Purchase #6	$77.98	13.287%	$88.3412	$88.34	$88.35	$88.30
Purchase #7	$152.90	9.558%	$167.5142	$167.51	$167.50	$167.50
7 purchase totals =	$1,058.30		$1,152.1998	$1,152.20	$1,152.20	$1,152.20