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	$226.36	7.621%	$243.6109	$243.61	$243.60	$243.60
Purchase #2	$228.32	6.572%	$243.3252	$243.33	$243.35	$243.30
Purchase #3	$165.49	3.426%	$171.1597	$171.16	$171.15	$171.20
Purchase #4	$98.62	6.328%	$104.8607	$104.86	$104.85	$104.90
Purchase #5	$37.33	12.726%	$42.0806	$42.08	$42.10	$42.10
Purchase #6	$58.33	12.872%	$65.8382	$65.84	$65.85	$65.80
Purchase #7	$51.48	7.189%	$55.1809	$55.18	$55.20	$55.20
7 purchase totals =	$865.93		$926.0562	$926.06	$926.10	$926.10