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	$55.27	11.401%	$61.5713	$61.57	$61.55	$61.60
Purchase #2	$13.50	13.542%	$15.3282	$15.33	$15.35	$15.30
Purchase #3	$10.81	3.334%	$11.1704	$11.17	$11.15	$11.20
Purchase #4	$52.64	11.174%	$58.522	$58.52	$58.50	$58.50
Purchase #5	$145.98	7.218%	$156.5168	$156.52	$156.50	$156.50
Purchase #6	$186.31	6.354%	$198.1481	$198.15	$198.15	$198.10
Purchase #7	$91.44	10.524%	$101.0631	$101.06	$101.05	$101.10
7 purchase totals =	$555.95		$602.3199	$602.32	$602.25	$602.30