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	$144.79	4.460%	$151.2476	$151.25	$151.25	$151.20
Purchase #2	$94.32	12.301%	$105.9223	$105.92	$105.90	$105.90
Purchase #3	$229.55	6.865%	$245.3086	$245.31	$245.30	$245.30
Purchase #4	$47.45	12.681%	$53.4671	$53.47	$53.45	$53.50
Purchase #5	$83.94	7.534%	$90.264	$90.26	$90.25	$90.30
Purchase #6	$22.57	13.595%	$25.6384	$25.64	$25.65	$25.60
Purchase #7	$161.67	12.641%	$182.1067	$182.11	$182.10	$182.10
7 purchase totals =	$784.29		$853.9547	$853.96	$853.90	$853.90