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	$38.59	6.310%	$41.025	$41.03	$41.05	$41.00
Purchase #2	$43.46	5.280%	$45.7547	$45.75	$45.75	$45.80
Purchase #3	$145.91	4.817%	$152.9385	$152.94	$152.95	$152.90
Purchase #4	$36.85	9.764%	$40.448	$40.45	$40.45	$40.40
Purchase #5	$32.29	12.768%	$36.4128	$36.41	$36.40	$36.40
Purchase #6	$223.78	9.610%	$245.2853	$245.29	$245.30	$245.30
Purchase #7	$49.96	4.464%	$52.1902	$52.19	$52.20	$52.20
7 purchase totals =	$570.84		$614.0545	$614.06	$614.10	$614.00