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	$156.44	9.757%	$171.7039	$171.70	$171.70	$171.70
Purchase #2	$91.34	5.447%	$96.3153	$96.32	$96.30	$96.30
Purchase #3	$113.93	12.470%	$128.1371	$128.14	$128.15	$128.10
Purchase #4	$42.46	5.460%	$44.7783	$44.78	$44.80	$44.80
Purchase #5	$72.71	6.723%	$77.5983	$77.60	$77.60	$77.60
Purchase #6	$37.67	10.453%	$41.6076	$41.61	$41.60	$41.60
Purchase #7	$127.88	12.690%	$144.108	$144.11	$144.10	$144.10
7 purchase totals =	$642.43		$704.2485	$704.26	$704.25	$704.20