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	$134.72	12.314%	$151.3094	$151.31	$151.30	$151.30
Purchase #2	$144.55	5.321%	$152.2415	$152.24	$152.25	$152.20
Purchase #3	$194.69	12.633%	$219.2852	$219.29	$219.30	$219.30
Purchase #4	$214.33	4.424%	$223.812	$223.81	$223.80	$223.80
Purchase #5	$84.83	13.740%	$96.4856	$96.49	$96.50	$96.50
Purchase #6	$37.99	11.102%	$42.2076	$42.21	$42.20	$42.20
Purchase #7	$140.88	4.801%	$147.6436	$147.64	$147.65	$147.60
7 purchase totals =	$951.99		$1,032.9849	$1,032.99	$1,033.00	$1,032.90