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	$228.60	5.773%	$241.7971	$241.80	$241.80	$241.80
Purchase #2	$80.82	13.165%	$91.46	$91.46	$91.45	$91.50
Purchase #3	$159.74	7.322%	$171.4362	$171.44	$171.45	$171.40
Purchase #4	$213.38	4.594%	$223.1827	$223.18	$223.20	$223.20
Purchase #5	$190.41	3.139%	$196.387	$196.39	$196.40	$196.40
Purchase #6	$141.99	7.526%	$152.6762	$152.68	$152.70	$152.70
Purchase #7	$102.70	3.481%	$106.275	$106.28	$106.30	$106.30
7 purchase totals =	$1,117.64		$1,183.2142	$1,183.23	$1,183.30	$1,183.30