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	$167.73	5.212%	$176.4721	$176.47	$176.45	$176.50
Purchase #2	$205.26	5.829%	$217.2246	$217.22	$217.20	$217.20
Purchase #3	$156.94	9.162%	$171.3188	$171.32	$171.30	$171.30
Purchase #4	$167.95	13.558%	$190.7207	$190.72	$190.70	$190.70
Purchase #5	$154.80	10.577%	$171.1732	$171.17	$171.15	$171.20
Purchase #6	$64.62	4.251%	$67.367	$67.37	$67.35	$67.40
Purchase #7	$142.99	6.801%	$152.7147	$152.71	$152.70	$152.70
7 purchase totals =	$1,060.29		$1,146.9911	$1,146.98	$1,146.85	$1,147.00