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	$167.58	4.716%	$175.4831	$175.48	$175.50	$175.50
Purchase #2	$162.86	3.639%	$168.7865	$168.79	$168.80	$168.80
Purchase #3	$51.59	11.371%	$57.4563	$57.46	$57.45	$57.50
Purchase #4	$144.72	4.579%	$151.3467	$151.35	$151.35	$151.30
Purchase #5	$129.84	6.537%	$138.3276	$138.33	$138.35	$138.30
Purchase #6	$176.41	8.279%	$191.015	$191.02	$191.00	$191.00
Purchase #7	$229.25	8.520%	$248.7821	$248.78	$248.80	$248.80
7 purchase totals =	$1,062.25		$1,131.1973	$1,131.21	$1,131.25	$1,131.20