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	$159.49	9.526%	$174.683	$174.68	$174.70	$174.70
Purchase #2	$11.89	9.515%	$13.0213	$13.02	$13.00	$13.00
Purchase #3	$8.32	3.180%	$8.5846	$8.58	$8.60	$8.60
Purchase #4	$206.69	7.221%	$221.6151	$221.62	$221.60	$221.60
Purchase #5	$89.48	10.134%	$98.5479	$98.55	$98.55	$98.50
Purchase #6	$33.91	13.482%	$38.4817	$38.48	$38.50	$38.50
Purchase #7	$52.88	11.818%	$59.1294	$59.13	$59.15	$59.10
7 purchase totals =	$562.66		$614.0630	$614.06	$614.10	$614.00