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	$190.33	6.663%	$203.0117	$203.01	$203.00	$203.00
Purchase #2	$118.57	3.759%	$123.027	$123.03	$123.05	$123.00
Purchase #3	$78.95	13.298%	$89.4488	$89.45	$89.45	$89.40
Purchase #4	$8.28	6.457%	$8.8146	$8.81	$8.80	$8.80
Purchase #5	$245.46	5.559%	$259.1051	$259.11	$259.10	$259.10
Purchase #6	$99.98	8.368%	$108.3463	$108.35	$108.35	$108.30
Purchase #7	$141.80	6.411%	$150.8908	$150.89	$150.90	$150.90
7 purchase totals =	$883.37		$942.6443	$942.65	$942.65	$942.50