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	$57.31	4.315%	$59.7829	$59.78	$59.80	$59.80
Purchase #2	$67.95	11.327%	$75.6467	$75.65	$75.65	$75.60
Purchase #3	$53.72	11.433%	$59.8618	$59.86	$59.85	$59.90
Purchase #4	$139.25	7.678%	$149.9416	$149.94	$149.95	$149.90
Purchase #5	$196.97	4.284%	$205.4082	$205.41	$205.40	$205.40
Purchase #6	$94.26	9.627%	$103.3344	$103.33	$103.35	$103.30
Purchase #7	$42.26	6.710%	$45.0956	$45.10	$45.10	$45.10
7 purchase totals =	$651.72		$699.0712	$699.07	$699.10	$699.00