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	$68.90	13.366%	$78.1092	$78.11	$78.10	$78.10
Purchase #2	$157.44	3.296%	$162.6292	$162.63	$162.65	$162.60
Purchase #3	$84.58	13.866%	$96.3079	$96.31	$96.30	$96.30
Purchase #4	$122.61	8.686%	$133.2599	$133.26	$133.25	$133.30
Purchase #5	$78.57	12.594%	$88.4651	$88.47	$88.45	$88.50
Purchase #6	$154.42	8.362%	$167.3326	$167.33	$167.35	$167.30
Purchase #7	$91.53	9.874%	$100.5677	$100.57	$100.55	$100.60
7 purchase totals =	$758.05		$826.6716	$826.68	$826.65	$826.70