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	$118.34	4.498%	$123.6629	$123.66	$123.65	$123.70
Purchase #2	$62.43	12.577%	$70.2818	$70.28	$70.30	$70.30
Purchase #3	$73.33	12.588%	$82.5608	$82.56	$82.55	$82.60
Purchase #4	$74.77	9.633%	$81.9726	$81.97	$81.95	$82.00
Purchase #5	$198.86	12.190%	$223.101	$223.10	$223.10	$223.10
Purchase #6	$41.83	9.845%	$45.9482	$45.95	$45.95	$45.90
Purchase #7	$242.68	4.342%	$253.2172	$253.22	$253.20	$253.20
7 purchase totals =	$812.24		$880.7445	$880.74	$880.70	$880.80