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	$41.29	9.732%	$45.3083	$45.31	$45.30	$45.30
Purchase #2	$79.98	3.514%	$82.7905	$82.79	$82.80	$82.80
Purchase #3	$119.82	4.224%	$124.8812	$124.88	$124.90	$124.90
Purchase #4	$149.78	12.810%	$168.9668	$168.97	$168.95	$169.00
Purchase #5	$171.96	7.155%	$184.2637	$184.26	$184.25	$184.30
Purchase #6	$243.96	7.868%	$263.1548	$263.15	$263.15	$263.20
Purchase #7	$128.54	6.235%	$136.5545	$136.55	$136.55	$136.60
7 purchase totals =	$935.33		$1,005.9198	$1,005.91	$1,005.90	$1,006.10