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	$33.57	10.416%	$37.0667	$37.07	$37.05	$37.10
Purchase #2	$222.57	10.150%	$245.1609	$245.16	$245.15	$245.20
Purchase #3	$204.87	5.711%	$216.5701	$216.57	$216.55	$216.60
Purchase #4	$231.89	5.742%	$245.2051	$245.21	$245.20	$245.20
Purchase #5	$23.79	6.370%	$25.3054	$25.31	$25.30	$25.30
Purchase #6	$116.95	11.355%	$130.2297	$130.23	$130.25	$130.20
Purchase #7	$72.54	8.571%	$78.7574	$78.76	$78.75	$78.80
7 purchase totals =	$906.18		$978.2953	$978.31	$978.25	$978.40