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	$94.76	8.746%	$103.0477	$103.05	$103.05	$103.00
Purchase #2	$25.89	4.241%	$26.988	$26.99	$27.00	$27.00
Purchase #3	$106.94	7.123%	$114.5573	$114.56	$114.55	$114.60
Purchase #4	$75.33	13.316%	$85.3609	$85.36	$85.35	$85.40
Purchase #5	$162.98	6.609%	$173.7513	$173.75	$173.75	$173.80
Purchase #6	$52.45	13.252%	$59.4007	$59.40	$59.40	$59.40
Purchase #7	$148.46	12.615%	$167.1882	$167.19	$167.20	$167.20
7 purchase totals =	$666.81		$730.2941	$730.30	$730.30	$730.40