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	$134.43	8.547%	$145.9197	$145.92	$145.90	$145.90
Purchase #2	$167.69	7.431%	$180.151	$180.15	$180.15	$180.20
Purchase #3	$196.67	12.556%	$221.3639	$221.36	$221.35	$221.40
Purchase #4	$133.30	3.419%	$137.8575	$137.86	$137.85	$137.90
Purchase #5	$167.68	8.239%	$181.4952	$181.50	$181.50	$181.50
Purchase #6	$9.56	13.782%	$10.8776	$10.88	$10.90	$10.90
Purchase #7	$162.87	7.147%	$174.5103	$174.51	$174.50	$174.50
7 purchase totals =	$972.20		$1,052.1752	$1,052.18	$1,052.15	$1,052.30