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	$192.28	4.318%	$200.5827	$200.58	$200.60	$200.60
Purchase #2	$218.59	3.498%	$226.2363	$226.24	$226.25	$226.20
Purchase #3	$55.48	13.515%	$62.9781	$62.98	$63.00	$63.00
Purchase #4	$145.28	13.745%	$165.2487	$165.25	$165.25	$165.20
Purchase #5	$29.88	11.331%	$33.2657	$33.27	$33.25	$33.30
Purchase #6	$131.30	9.370%	$143.6028	$143.60	$143.60	$143.60
Purchase #7	$215.40	3.722%	$223.4172	$223.42	$223.40	$223.40
7 purchase totals =	$988.21		$1,055.3315	$1,055.34	$1,055.35	$1,055.30