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	$7.84	5.814%	$8.2958	$8.30	$8.30	$8.30
Purchase #2	$172.81	5.614%	$182.5116	$182.51	$182.50	$182.50
Purchase #3	$85.57	4.550%	$89.4634	$89.46	$89.45	$89.50
Purchase #4	$66.26	3.768%	$68.7567	$68.76	$68.75	$68.80
Purchase #5	$54.82	13.463%	$62.2004	$62.20	$62.20	$62.20
Purchase #6	$104.56	5.663%	$110.4812	$110.48	$110.50	$110.50
Purchase #7	$216.89	11.362%	$241.533	$241.53	$241.55	$241.50
7 purchase totals =	$708.75		$763.2421	$763.24	$763.25	$763.30