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	$78.36	5.352%	$82.5538	$82.55	$82.55	$82.60
Purchase #2	$168.30	12.597%	$189.5008	$189.50	$189.50	$189.50
Purchase #3	$166.90	8.650%	$181.3369	$181.34	$181.35	$181.30
Purchase #4	$197.40	13.272%	$223.5989	$223.60	$223.60	$223.60
Purchase #5	$145.95	10.116%	$160.7143	$160.71	$160.70	$160.70
Purchase #6	$50.39	8.648%	$54.7477	$54.75	$54.75	$54.70
Purchase #7	$243.44	8.150%	$263.2804	$263.28	$263.30	$263.30
7 purchase totals =	$1,050.74		$1,155.7328	$1,155.73	$1,155.75	$1,155.70