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	$246.29	12.359%	$276.729	$276.73	$276.75	$276.70
Purchase #2	$235.34	3.416%	$243.3792	$243.38	$243.40	$243.40
Purchase #3	$98.80	3.655%	$102.4111	$102.41	$102.40	$102.40
Purchase #4	$156.30	3.730%	$162.13	$162.13	$162.15	$162.10
Purchase #5	$97.81	12.352%	$109.8915	$109.89	$109.90	$109.90
Purchase #6	$60.34	8.532%	$65.4882	$65.49	$65.50	$65.50
Purchase #7	$142.88	5.699%	$151.0227	$151.02	$151.00	$151.00
7 purchase totals =	$1,037.76		$1,111.0517	$1,111.05	$1,111.10	$1,111.00