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	$125.48	13.817%	$142.8176	$142.82	$142.80	$142.80
Purchase #2	$204.88	13.265%	$232.0573	$232.06	$232.05	$232.10
Purchase #3	$229.40	6.578%	$244.4899	$244.49	$244.50	$244.50
Purchase #4	$80.56	6.638%	$85.9076	$85.91	$85.90	$85.90
Purchase #5	$52.73	13.292%	$59.7389	$59.74	$59.75	$59.70
Purchase #6	$45.44	3.715%	$47.1281	$47.13	$47.15	$47.10
Purchase #7	$136.79	11.395%	$152.3772	$152.38	$152.40	$152.40
7 purchase totals =	$875.28		$964.5166	$964.53	$964.55	$964.50