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	$179.76	3.354%	$185.7892	$185.79	$185.80	$185.80
Purchase #2	$189.42	10.717%	$209.7201	$209.72	$209.70	$209.70
Purchase #3	$7.90	4.610%	$8.2642	$8.26	$8.25	$8.30
Purchase #4	$80.75	10.444%	$89.1835	$89.18	$89.20	$89.20
Purchase #5	$197.80	9.263%	$216.1222	$216.12	$216.10	$216.10
Purchase #6	$51.63	9.192%	$56.3758	$56.38	$56.40	$56.40
Purchase #7	$28.29	11.263%	$31.4763	$31.48	$31.50	$31.50
7 purchase totals =	$735.55		$796.9313	$796.93	$796.95	$797.00