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	$90.75	11.593%	$101.2706	$101.27	$101.25	$101.30
Purchase #2	$51.95	3.372%	$53.7018	$53.70	$53.70	$53.70
Purchase #3	$162.44	13.556%	$184.4604	$184.46	$184.45	$184.50
Purchase #4	$181.56	5.117%	$190.8504	$190.85	$190.85	$190.90
Purchase #5	$54.76	4.829%	$57.4044	$57.40	$57.40	$57.40
Purchase #6	$211.62	12.522%	$238.1191	$238.12	$238.10	$238.10
Purchase #7	$122.84	9.432%	$134.4263	$134.43	$134.45	$134.40
7 purchase totals =	$875.92		$960.2330	$960.23	$960.20	$960.30