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	$41.71	5.632%	$44.0591	$44.06	$44.05	$44.10
Purchase #2	$51.91	3.683%	$53.8218	$53.82	$53.80	$53.80
Purchase #3	$63.33	6.315%	$67.3293	$67.33	$67.35	$67.30
Purchase #4	$196.70	8.316%	$213.0576	$213.06	$213.05	$213.10
Purchase #5	$40.84	4.216%	$42.5618	$42.56	$42.55	$42.60
Purchase #6	$240.82	11.351%	$268.1555	$268.16	$268.15	$268.20
Purchase #7	$42.56	9.188%	$46.4704	$46.47	$46.45	$46.50
7 purchase totals =	$677.87		$735.4555	$735.46	$735.40	$735.60