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	$91.94	6.647%	$98.0513	$98.05	$98.05	$98.10
Purchase #2	$238.39	12.470%	$268.1172	$268.12	$268.10	$268.10
Purchase #3	$71.90	7.650%	$77.4004	$77.40	$77.40	$77.40
Purchase #4	$100.37	10.837%	$111.2471	$111.25	$111.25	$111.20
Purchase #5	$46.48	9.248%	$50.7785	$50.78	$50.80	$50.80
Purchase #6	$115.47	3.524%	$119.5392	$119.54	$119.55	$119.50
Purchase #7	$180.71	7.427%	$194.1313	$194.13	$194.15	$194.10
7 purchase totals =	$845.26		$919.2650	$919.27	$919.30	$919.20