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	$110.52	11.415%	$123.1359	$123.14	$123.15	$123.10
Purchase #2	$180.76	3.179%	$186.5064	$186.51	$186.50	$186.50
Purchase #3	$47.73	8.756%	$51.9092	$51.91	$51.90	$51.90
Purchase #4	$241.36	9.103%	$263.331	$263.33	$263.35	$263.30
Purchase #5	$31.62	3.814%	$32.826	$32.83	$32.85	$32.80
Purchase #6	$77.50	5.298%	$81.606	$81.61	$81.60	$81.60
Purchase #7	$49.63	9.654%	$54.4213	$54.42	$54.40	$54.40
7 purchase totals =	$739.12		$793.7358	$793.75	$793.75	$793.60