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	$153.60	11.502%	$171.2671	$171.27	$171.25	$171.30
Purchase #2	$85.67	3.732%	$88.8672	$88.87	$88.85	$88.90
Purchase #3	$86.50	3.765%	$89.7567	$89.76	$89.75	$89.80
Purchase #4	$28.25	13.331%	$32.016	$32.02	$32.00	$32.00
Purchase #5	$43.53	12.812%	$49.1071	$49.11	$49.10	$49.10
Purchase #6	$222.84	10.109%	$245.3669	$245.37	$245.35	$245.40
Purchase #7	$44.25	11.116%	$49.1688	$49.17	$49.15	$49.20
7 purchase totals =	$664.64		$725.5498	$725.57	$725.45	$725.70