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	$158.51	8.110%	$171.3652	$171.37	$171.35	$171.40
Purchase #2	$191.33	4.825%	$200.5617	$200.56	$200.55	$200.60
Purchase #3	$6.37	12.557%	$7.1699	$7.17	$7.15	$7.20
Purchase #4	$196.27	12.716%	$221.2277	$221.23	$221.25	$221.20
Purchase #5	$37.73	13.669%	$42.8873	$42.89	$42.90	$42.90
Purchase #6	$129.47	3.294%	$133.7347	$133.73	$133.75	$133.70
Purchase #7	$90.76	12.253%	$101.8808	$101.88	$101.90	$101.90
7 purchase totals =	$810.44		$878.8273	$878.83	$878.85	$878.90