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	$167.26	3.774%	$173.5724	$173.57	$173.55	$173.60
Purchase #2	$60.49	11.159%	$67.2401	$67.24	$67.25	$67.20
Purchase #3	$139.78	3.626%	$144.8484	$144.85	$144.85	$144.80
Purchase #4	$53.98	3.600%	$55.9233	$55.92	$55.90	$55.90
Purchase #5	$86.47	3.407%	$89.416	$89.42	$89.40	$89.40
Purchase #6	$207.50	3.755%	$215.2916	$215.29	$215.30	$215.30
Purchase #7	$228.98	7.325%	$245.7528	$245.75	$245.75	$245.80
7 purchase totals =	$944.46		$992.0446	$992.04	$992.00	$992.00