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	$168.70	10.414%	$186.2684	$186.27	$186.25	$186.30
Purchase #2	$198.65	12.163%	$222.8118	$222.81	$222.80	$222.80
Purchase #3	$147.90	13.415%	$167.7408	$167.74	$167.75	$167.70
Purchase #4	$28.64	6.738%	$30.5698	$30.57	$30.55	$30.60
Purchase #5	$123.91	10.519%	$136.9441	$136.94	$136.95	$136.90
Purchase #6	$216.82	10.201%	$238.9378	$238.94	$238.95	$238.90
Purchase #7	$207.71	4.498%	$217.0528	$217.05	$217.05	$217.10
7 purchase totals =	$1,092.33		$1,200.3255	$1,200.32	$1,200.30	$1,200.30