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	$168.75	9.322%	$184.4809	$184.48	$184.50	$184.50
Purchase #2	$115.81	9.290%	$126.5687	$126.57	$126.55	$126.60
Purchase #3	$100.49	5.726%	$106.2441	$106.24	$106.25	$106.20
Purchase #4	$71.92	13.370%	$81.5357	$81.54	$81.55	$81.50
Purchase #5	$94.67	7.516%	$101.7854	$101.79	$101.80	$101.80
Purchase #6	$179.63	9.198%	$196.1524	$196.15	$196.15	$196.20
Purchase #7	$249.52	6.531%	$265.8162	$265.82	$265.80	$265.80
7 purchase totals =	$980.79		$1,062.5834	$1,062.59	$1,062.60	$1,062.60