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	$52.62	3.506%	$54.4649	$54.46	$54.45	$54.50
Purchase #2	$31.95	6.615%	$34.0635	$34.06	$34.05	$34.10
Purchase #3	$66.27	8.811%	$72.109	$72.11	$72.10	$72.10
Purchase #4	$202.41	8.367%	$219.3456	$219.35	$219.35	$219.30
Purchase #5	$92.62	12.466%	$104.166	$104.17	$104.15	$104.20
Purchase #6	$240.33	9.613%	$263.4329	$263.43	$263.45	$263.40
Purchase #7	$39.54	12.809%	$44.6047	$44.60	$44.60	$44.60
7 purchase totals =	$725.74		$792.1866	$792.18	$792.15	$792.20