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	$162.46	11.755%	$181.5572	$181.56	$181.55	$181.60
Purchase #2	$190.89	9.279%	$208.6027	$208.60	$208.60	$208.60
Purchase #3	$189.47	13.645%	$215.3232	$215.32	$215.30	$215.30
Purchase #4	$157.61	11.608%	$175.9054	$175.91	$175.90	$175.90
Purchase #5	$80.54	12.629%	$90.7114	$90.71	$90.70	$90.70
Purchase #6	$45.30	8.441%	$49.1238	$49.12	$49.10	$49.10
Purchase #7	$44.91	11.851%	$50.2323	$50.23	$50.25	$50.20
7 purchase totals =	$871.18		$971.4560	$971.45	$971.40	$971.40