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	$112.88	10.218%	$124.4141	$124.41	$124.40	$124.40
Purchase #2	$163.71	12.428%	$184.0559	$184.06	$184.05	$184.10
Purchase #3	$174.34	10.576%	$192.7782	$192.78	$192.80	$192.80
Purchase #4	$104.31	4.790%	$109.3064	$109.31	$109.30	$109.30
Purchase #5	$72.58	8.703%	$78.8966	$78.90	$78.90	$78.90
Purchase #6	$18.30	11.164%	$20.343	$20.34	$20.35	$20.30
Purchase #7	$202.77	6.194%	$215.3296	$215.33	$215.35	$215.30
7 purchase totals =	$848.89		$925.1238	$925.13	$925.15	$925.10