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	$120.75	5.465%	$127.349	$127.35	$127.35	$127.30
Purchase #2	$25.61	12.179%	$28.729	$28.73	$28.75	$28.70
Purchase #3	$90.79	10.637%	$100.4473	$100.45	$100.45	$100.40
Purchase #4	$202.33	10.376%	$223.3238	$223.32	$223.30	$223.30
Purchase #5	$129.62	3.797%	$134.5417	$134.54	$134.55	$134.50
Purchase #6	$118.43	10.743%	$131.1529	$131.15	$131.15	$131.20
Purchase #7	$85.96	4.851%	$90.1299	$90.13	$90.15	$90.10
7 purchase totals =	$773.49		$835.6736	$835.67	$835.70	$835.50