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	$134.60	5.627%	$142.1739	$142.17	$142.15	$142.20
Purchase #2	$236.90	7.410%	$254.4543	$254.45	$254.45	$254.50
Purchase #3	$170.25	3.295%	$175.8597	$175.86	$175.85	$175.90
Purchase #4	$203.79	9.744%	$223.6473	$223.65	$223.65	$223.60
Purchase #5	$146.62	12.461%	$164.8903	$164.89	$164.90	$164.90
Purchase #6	$224.40	9.385%	$245.4599	$245.46	$245.45	$245.50
Purchase #7	$135.47	4.647%	$141.7653	$141.77	$141.75	$141.80
7 purchase totals =	$1,252.03		$1,348.2507	$1,348.25	$1,348.20	$1,348.40