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	$20.51	8.794%	$22.3136	$22.31	$22.30	$22.30
Purchase #2	$6.83	6.224%	$7.2551	$7.26	$7.25	$7.30
Purchase #3	$96.60	7.820%	$104.1541	$104.15	$104.15	$104.20
Purchase #4	$44.31	13.571%	$50.3233	$50.32	$50.30	$50.30
Purchase #5	$110.84	3.146%	$114.327	$114.33	$114.35	$114.30
Purchase #6	$147.59	13.709%	$167.8231	$167.82	$167.80	$167.80
Purchase #7	$89.29	11.688%	$99.7262	$99.73	$99.75	$99.70
7 purchase totals =	$515.97		$565.9224	$565.92	$565.90	$565.90