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	$67.76	3.718%	$70.2793	$70.28	$70.30	$70.30
Purchase #2	$204.81	7.181%	$219.5174	$219.52	$219.50	$219.50
Purchase #3	$98.80	10.452%	$109.1266	$109.13	$109.15	$109.10
Purchase #4	$150.27	11.589%	$167.6848	$167.68	$167.70	$167.70
Purchase #5	$226.75	6.399%	$241.2597	$241.26	$241.25	$241.30
Purchase #6	$135.83	11.616%	$151.608	$151.61	$151.60	$151.60
Purchase #7	$7.52	4.815%	$7.8821	$7.88	$7.90	$7.90
7 purchase totals =	$891.74		$967.3579	$967.36	$967.40	$967.40