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	$115.78	4.197%	$120.6393	$120.64	$120.65	$120.60
Purchase #2	$164.36	4.579%	$171.886	$171.89	$171.90	$171.90
Purchase #3	$215.72	6.416%	$229.5606	$229.56	$229.55	$229.60
Purchase #4	$183.37	4.781%	$192.1369	$192.14	$192.15	$192.10
Purchase #5	$43.79	4.186%	$45.623	$45.62	$45.60	$45.60
Purchase #6	$211.41	3.677%	$219.1835	$219.18	$219.20	$219.20
Purchase #7	$152.77	8.543%	$165.8211	$165.82	$165.80	$165.80
7 purchase totals =	$1,087.20		$1,144.8504	$1,144.85	$1,144.85	$1,144.80