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	$170.96	11.524%	$190.6614	$190.66	$190.65	$190.70
Purchase #2	$203.30	7.751%	$219.0578	$219.06	$219.05	$219.10
Purchase #3	$93.85	12.781%	$105.845	$105.85	$105.85	$105.80
Purchase #4	$23.34	9.854%	$25.6399	$25.64	$25.65	$25.60
Purchase #5	$205.74	8.586%	$223.4048	$223.40	$223.40	$223.40
Purchase #6	$141.31	3.553%	$146.3307	$146.33	$146.35	$146.30
Purchase #7	$153.77	7.810%	$165.7794	$165.78	$165.80	$165.80
7 purchase totals =	$992.27		$1,076.7190	$1,076.72	$1,076.75	$1,076.70