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	$205.59	10.503%	$227.1831	$227.18	$227.20	$227.20
Purchase #2	$181.28	10.477%	$200.2727	$200.27	$200.25	$200.30
Purchase #3	$61.74	9.473%	$67.5886	$67.59	$67.60	$67.60
Purchase #4	$114.56	12.414%	$128.7815	$128.78	$128.80	$128.80
Purchase #5	$79.48	3.499%	$82.261	$82.26	$82.25	$82.30
Purchase #6	$9.57	8.539%	$10.3872	$10.39	$10.40	$10.40
Purchase #7	$68.57	11.473%	$76.437	$76.44	$76.45	$76.40
7 purchase totals =	$720.79		$792.9111	$792.91	$792.95	$793.00